The invention relates to a burner nozzle comprising an outer body having a longitudinal hole therethrough, a nozzle body which is inserted in the end portion of the longitudinal hole and has a coaxial nozzle orifice, with a vortex pocket provided at the inner end of the nozzle orifice communicating, through at least one channel, with a first annular cavity extending at the outer end of the channel or channels, and a pin which is inserted in the longitudinal hole of the outer body and bounds a passage for supplying fuel to the nozzle body.
From Swiss Pat. No. 553,379, there is known an oil burner with a burner nozzle comprising an axially symmetrical outer body tapering toward the nozzle tip. In the tip of the outer body, a nozzle plate is inserted having a nozzle orifice at its center. Adjoining the nozzle plate is a vortex body whose contacting surface is provided with channels which extend from the outer edge of the vortex body to the area of the nozzle orifice. The vortex body is pressed into contact with the nozzle plate by a hollow pin which is snugly screwed into the outer body. An annular gap is provided between the front end of the pin and of the vortex body and the inside surface of the outer body. On its front end, the pin is further provided with slots through which, during operation, the oil can flow from the oblong hole of the pin into said annular gap. Then, the oil flows through the slot to the outer ends of the channels provided in the vortex body. The pin end remote from the nozzle plate is provided with radial bores opening into the oblong hole thereof. In the zone of these radial bores, the pin is surrounded by a fine-meshed screen. During operation, the oil passes through the screen serving as filter and through the radial bores into the oblong hole of the pin.
Thus, during operation of this prior art burner nozzle, the oil is filtered through the screen surrounding the rear portion of the pin. Experience has shown, however, that in spite of this arrangement, dirt still passes to the channels of the vortex body and may cause their clogging. This is the case particularly with burner nozzles which are intended for relatively low heating capacities and in which the channels of the vortex body have correspondingly small sectional areas. For example, for heating equipments of small single-family houses, and of vehicles, burners are needed in which the channels have widths and depths in the magnitude of 0.12 to 0.3 mm.
Attempts have already been made to prevent a clogging of the channels by providing a collar at the front end of the pin of the prior art burner disclosed in Swiss Pat. No. 553,379. The collar has been dimensioned to obtain a radial width of the annular gap between the inside surface of the outer body and the collar, in the zone of the collar,in the magnitude of 0.1 mm, so that dirt particles also be held back. This design of the oil burner did reduce the frequency of clogging the channels. However, tests have shown that dirt particles, particularly fibre-like particles, still penetrate to the channels of the vortex body and may cause clogging. Further known, from German Offenlegungschrift No. 24 41 833, is a burner nozzle having a hollow outer body in which, at one of its ends, a substantially disc-shaped body and a vortex body with a channel for producing turbulence are inserted. On the vortex body side remote from the nozzle body, a hollow bolt with a stepped outer surface is provided which is screwed into the outer body. An annular gap is provided between the outer surfaces of the nozzle body, of the vortex body, and of the adjoining end of the hollow bolt and the inside surface of the outer body. The bolt end adjoining the vortex body is provided with radial ports connecting the cavity to the annular gap. A filter in the form of a cylindrical sleeve surrounds the bolt end provided with the radial ports, the vortex body, as well as a portion of the nozzle body, and applies against their outer surfaces. The oil to be burned is supplied through the hollow of the bolt and passes through the radial ports of the bolt and said annular gap into the channel of the vortex body, and is to be filtered by the filter.
The filter of a burner nozzle designed in accordance with the German Offenlegunschrift No. 24 41 833 and known to the inventor is made from a metal gauze which certainly is cut out of a piece of gauze and then welded to a sleeve. Thus, the prior art burner nozzle has the disadvantage that a separate filter must be made of a wire mesh and engaged on the nozzle body, the vortex body, and the end of the bolt. Since the filter must be very fine-meshed to perform its function, its manufacture and engagement on the parts is relatively time consuming and very exacting. In addition, it is hardly possible to engage the filter on the nozzle body, the vortex body, and the bolt in such a way as to ensure everywhere a close fit and to prevent dirt particles from escaping past the filter edges. In particular, since the filter is provided with a weld which necessarily increases thickness and causes rigidity, there is a great chance that the filter will not perfectly apply in the area of the weld and that dirt particles will there be allowed to escape. Moreover, the weld itself also may have defective spots where dirt particles may penetrate through. Further, there is a considerable risk that during the cutting of the wire mesh and engaging of the filter, the wires forming the filter will partly be cut through or otherwise damaged and that later, during operation, wire lengths will break off and clog the channel of the vortex body.
Another disadvantage of the burner nozzle known from German Offenlegungschrift No. 24 41 833 results from the fact that the heating oil usually contains semi-solid, paraffinic particles. In general, these particles are about ball-shaped and may temporarily be deformed. While temporarily so deformed, they might pass through an aperture of a lattice filter, even though in their initial spherical shape, they have a diameter exceeding the size of the filter aperture. If such particles pass into a channel serving to produce turbulence and having a clear cross section smaller than the ball diameter, but being substantially longer than the ball diameter, particles frequently can no longer deform to a sufficient extent to pass through the channel and cause clogging.